Well drilling equipment



March 18, 1958 J. G. SCOTT ETAL WELL DRILLING EQUIPMENT FiledvAug. 27,1954 '7 Sheets-Sheet l INVENTORY JflMf-Y 6'. SCOTT ROLAND A. FREEMANREESE T HOUSTON HTTORNEYJ' March 18, 1958 J. G. SCOTT ET AL WELLDRILLING EQUIPMENT 7 Sheets-Sheet 4 Filed Aug. 27, 1954 .FIIE EEINVENTORS JflMES 6. 5CO7'7' ROLAND H. FEE'EMHN BY E5555 7'- HOUSTONMarch 18, 1958 J. G. scoTT ET AL 2,

' WELL DRILLING EQUIPMENT Filed Aug. 27, 1954 vsneets-sheet 5 INVENTORSJAMES G. 56077 QOLHND A. FREEMAN y E5555 7'. HOUSTON ATTOE/VE Yf March18, 1958 J. G. SCOTT ETAL WELL DRILLING EQUIPMENT 7 Sheets-Sheet '7Filed Aug. 27, 1954 Fl E E INVENTORS JAMES a. 5c07'7 ROL AND H.FREE'MAA/ BY REESE 7.'/-/0U.$7'0N HTTOENL' Y5 United States PatentC WELLDRILLING EQUIPIWENT James G. Scott, Simi, Roland A. Freeman, SantaMonica,

and Reese T. Houston, Simi, Califi, assignors to American PercussionTool Company, San" Francisco, Calif a corporation of CaliforniaApplication August 27,1954, SerialNo. 452,522

7 Claims. (Cl. 2554.4)

This inventionrelates generally to the drilling of oil,

gas, water or like earth wells, and to equipment for such drillingoperation.

In our co-pending application Serial No. 445,666,

filed July 26, 1954, and entitled Well Drilling Equipment and Method,there is disclosed drilling equipment employing a rotary drill head andan electrical actuatoradapted to apply impact to the head at a constantirequency. The housing which carries the rotary head and mounts theactuating means is adapted to be attachedto the lowercnd or" a rotarydrill stem. Inoperation the drill stem is rotated in accordance withconventional,

rotary earth drilling practice, the actuator is energized to applyimpacts to the drill head to thereby efiect percussion drilling, andatthe same time rotary mud is circulated through the head for theremoval of cuttings. In

some instances it is not desirable to employ a conven-.

tional "drill stem, together with other parts of a conventional rotarydrillingequipment, including the table 7 at the surface of the well forturning thevstem.-

It is an object of the present invention to providea drilling equipmentand method making use of thGiIlVfiIltion disclosed in said copendingapplication, but which incorporates all of the operating parts in anassembly which can be lowered into a well by a cable.

Another object of the invention is to provide novel equipment of theabove character which provides for,

the circulation of rotary drilling mud within the well.

Another object of the invention is to provide equipment of the abovecharacter in the form of a self-contained assembly adapted to be loweredinto a well to carry out efiicient and rapid cutting byimpacterpercussion action, while at the-same time including means for rotatingthe head uponthe formation,-for circulating drilling mud, and for thecontinual removal of cuttings from the area of the drill head.

Additional objects and features of the inventionwill appear from thefollowing description in which the preferred embodiment has been setforth in-detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure l is a side el'evational view partly in section,

schematically illustrating an earth well with our equipment beingemployed for drilling operations.

Figures 2A to 21, inclusive, taken together, form-a side elevationalview in section illustrating the upper part of a complete assembly whichis lowered into the. wellfor drilling operations.

- the bar 34, and a recoil spring.- As shown particularly in Figures 21and 2] this structureconsists of concentric gether. illustrate equipment-as disclosed in our aforementioned copending application. The drillinghead 10 in this inerates at the bottom of the Well, and which carries adrill head 10. The assembly 9 is carried at the lower end of a cable8,-which extends down from the surface of the well,-and which at thewell surface is passed over suitable, means such as the conventionalcrown block 13 of awell derrick, and wound on a drum H.

Assembly 9 is illustrated in Figures 2A-2J takeneto- Referring first toFigure 2H, 21 and 2], they stance consists generally of a body 16carrying aplurality of toothed rotary cutter assemblies 17. Suchdrilling heads are yaell kuown -to those familiar with oil and-gas Idrilling methods, -and-are manufactured in various types 15' and sizesfor different kinds' of drilling conditions. The threaded shank -18ofthe head is. engaged with the head mounting member-'19, which in turnis located within the lower part'of the tubular housing '11. The lowerannular portion-20 0f member 19 is slidably. received in the bushing 21,which can be made. ofsuitable materiah such as -bronze.- A suitabletorque transmitting connectioniis formed between these parts, and mayconsist of a plurality-of splines. 22 :formed on the member 19andslidably engaging slots-23 'formed in the bushing 21. Thebushing--21:is'.attached by suitable means such .as the screws 24 tothering .26, the latterbeing suitably secured, .as by welding, tothe lowerend of the housing 11.

A..suitable.seal is formed between the head and the ring 26-.to .prevententrance. of mud or cuttings. For this purpose we have shown a diaphragm27 of flexible material suchv as fabric reinforced-natural ,orsyntheticrubber having;its v.inner peripheral edge. clamped, to. a gasket ring28, .and its outer marginclampedbetweenthe end piece of. the ring 26 andthe annular washer -29. The

,clampingwasher 29is held in placebyothe ring;-31,

which is internally threaded andengagedwith the threaded exterior ofring,26.; The inner marginof the gasketring 28, is tightly clampedbetween theshoulder 32 ;on;the head and the opposed end face.33,ofmember 19.

Theupper end of the member-19 isattacheddo; the impact ;transmitting bar34 which extends: concentric with the axis of the housing .11. ,As willbe presently explained it is the upper end 'of this bar-that receivesimpacts from the electrical actuator.

Interposed between the member-19 and-theelectrical actuator there is astructure including guide means for is shown communicating with aplurality of pipe fittings 43, which in turn are connected by theflexible hose sections 44.with pipe fittings 46.. The latter. fittingsdirectly connect throughthe member 19 to deliver mud. into the space 42.In. accordance .withncustomarypractice .the

. cutter head is provided with ducts (not shown) which conduct the mudtothe area being drilled, whereby chips or cuttings are removed.

The bar 34 is slidably fitted. within the ,bushing 47, which in turnisfitted within the end casting 48. This casting has a lower flange 43which is clamped to the flange 51 on the lower end of tube 37, bysuitable means suchas the screws 53.v Suitable lubricant sealing meanssuch as the resilientO-ring seals 54 and 5-6, can be provided at theupper and lowerends of the bushing 47. Also suitable fittings 57 can beprovided for the introduction of lubricant.

. elo r end ca i aafiss u n e e nn o y s, and the latter is bored andfitted with the bushing 59.

The upper end of body 58 is provided with a flange 61 that overlies thering 38.

w The-members 48 and- 59 provide spaceforaccommoto the drill head,shoulder 67 is urged against the opposed face of the collar 63, by theforce of the loaded spring 62.

The upper part 69 of the rod 34 forms what can be referred to as ananvil portion. It is slidably fitted within a bushing 71 that is carriedby the sleeve 72. The sleeve 72 is assembled within abore 73" formed inthe upper part of member 58, and is provided with a flange 74 adapted toseat upon the cooperating shoulder face 76. The flange 74 is urgedagainst the shoulder face 76 by suitable means such as a Bellevillewasher 77. A suitable arrangement of ducts 78 and 79 can be provided forintroducing lubricant to the area between the bushing 71 and the anvilportion 69. V

The electrical actuator is preferably constructed as follows: It employsa field comprising two electromagnet assemblies 12a and 12b, which serveto operate a central piston-like'core 81. The assemblies 12a and 12b caneach consist of laminated cores 82 disposed radially about the axis ofthe central core,'and provided with windings 83.

' The pole pieces 84 and 86 of each laminated core terminate at theboundary of a cylindrical passage 87, within which the central core 81operates. The two sets of lami-' nated cores are shown separated by themounting plate 88, and have their outer portions set interposed betweenthe the finer s int rposed between the two sets of pole pieces 86. a I IThe central p1ston-like core 81 is. provided with lower and upper axialextensions 94 and 95 of reduced diameter which form impact or hammerelements. The hammer 'felement 94 delivers impacts to the'anvil portion69 of the bar 34. A bearing assembly for element 95 can consistof inspaced relationship with the plate 106 by the tubular shroud 113and theinterposed plate 114. The inner margin of the plate 114 forms anabutment shoulder 115 for the thrust receiving member 168.

As will be presently explained the windings of the electiomagnetassemblies are energized by current pulsations whereby the central core81 is caused to reciprocate a predetermined-number of complete strokesper minute. The weight of the moving parts, the strength and pre-loadingof the recoil springs, and the frequency of excitation of the windingsis such that the core reciprocates at a constant frequency. When nodownward force is being applied to the drill head, the force of thedownward stroke of the core is absorbed by the lower recoil spring 62;However as the load is applied to the head an increasing amount of theimpact energy is transmitted through the bar 34 to the head and to theformation, until a maximum optimum loading is reached, which is equal tothe force-of. the

loaded spring 62. By way of example this may be of the order of 30,000pounds.

A suitable circuit arrangement for exciting the windings of theelectromagnet assemblies is 'shown in Figure 6.

The lines L1 and L2 are connected to a suitable source ofalternatingcurrent, such as 150 volts at 30 cycles at lines through an electricalcable which extends concenthe surface of the well. The power isdeliveredto-the trio with the cable 3 through the assembly, the mudmotor 13, and either member 143 or 147 (the latter portion of the pathnot shown in the drawing). The windings 83 have a common point ofconnection which connects with l oneiline L1. The other terminals of thewindings 83 n connect with the rectifiers 116, which have a common pointfof connection to the other line L2. With this arrangement i rectifyingpulses are supplied alternately to the two sets in the 'upper portion ofthe main tubular housing 11. The lower closure 119 for the housing 118can be proa sleeve 96 which is mounted upon the laminated cores for suchas ducts 98, for introducing lubricant.

Here again the bushing can be provided with lubricant receiving ducts102. At its lower end face the bushing 101 is in direct engagement withthe'upper end face of f the sleeve 72. Also the lubricant ducts 102 canbe in communication with'ducts 78. V

Overlying the upper electromagnet assembly 12a there is an annular plate106 that is fitted within the channels 89. Above this plate there is asecond recoil spring 107 and mounting means for the same. The lower endof spring 107 seats upon the impact receiving member 108,

which has its end face 169 aligned with and opposed to the end face ofthe impact element 95. The member 108 is guided by'the bushing ring 111,which is fitted inthe upperportion of the sleeve The upper end of; thespring 107 seats upon a member 112, which is maintained of windings,whereby for a current frequency of 30 cycles per second, the centralcore 81 is reciprocated at a frequency of 3600 complete strokes perminute, thus delivering 1800 impacts per minute. The rectifiers 116 maybe of the dry seleniumtype, the mercury vapor type, or any other typesuitable for the current carrying capacity required.

Referring again to Figures 2H and 21, rectifier units 116 of the dryselenium type are shown disposed within a space 117 provided for thispurpose. This space is formed within a tubular housing 118 that isdisposed vided with a sealed fitting 121 to accommodate the conductingwires leading to -thev windings of the electro- .magnet assemblies. Alsothe end member 119 hasa' rigid sealed connection with. the member 112.

Thus member112 has an upwardly extending cylindrical portion 122, whichhas a threaded engagement 123 with a depending cylindrical portion 124of the end closure 119;

. Suitable means such as the 0-ringseals126 provides.

fluid tight seal'between these, parts. The upper ends of channels 89 areattached to thelower edge of a tubular section 127 that surrounds thetubular portion 122, and

which abuts the lower end face of the tubular portion 124. Also a portedseating ring 128 can be provided about the tubular section 127," andagainst which this a section may seat.

' To maintain the parts-of the electrical actuator in 'assembledrelatio'nywe haveshown a plurality of tie bolts 129, which at one endengage the member 113, and at the other end engage the member 58.'

. 1332 reference to 'Figure 21' it will be seen that the angular passage91 for circulating mud continues up- -wardly.past.the.closed housing118' to the space 131 which overliesthe'upper end :132 of the housing118. 'Space'131communicates' with thelower end of that part of thecomplete assembly illustratedinFigures ZA ZG, inclusive.

Referring now to FiguresZ'A-QG, inclusive, they show an upper couplerpart'136 for'making connection'with meat gene the, suspending cable, abailer 137 for; the removal f cuttings, a pump 152 for the circulation,of drilling mud, and a mud motor 138 for driving the lower partaoftheequipment, namely that part illustrated in Figures 21-1-21, inclusive.

Referringparticularly to that .part,of the assembly illustrated inFigure2G, the drive means. 138,consists of a suitablefluid pressureoperatedmotor-141 whichis mounted Within the tubular housing .142. This motorcan be one of the positive displacement type suitable, for operationondrilling mud.- At the lower end of the housing 142.there is a closure143 which servesto journal the central rotatable shaft 144. This; shaftis operably connected to the drive shaft of the motor 141, as by meansofsuitable speed reductiongearing 146. The shaft is internally threadedas illustrated in Figure 26, thereby enabling it to be coupled .upon the.male coupling part 147, formed at. the upper end of the assembly shownin Figure 21-1. The upper end of the motor iscoupled to the mud piping147a, whereby drilling mud is delivered to the motor from the pumpingmeans presently described. At the other end of the motor there is adirect coupling from the motor discharge ports to the passage throughthe shaft 144, whereby the mud is delivered into the space 131 of thatpart of theassembly illustrated in Figure 2H.

The pumping means 137 illustrated particularly in Figures 2D, 2E and 2Fconsists of an electrical motor 151, together with a multistagecentrifugal pump 152. The electric motor can be of any suitableconstruction but should be designed toprovide the necessary powertogether with compactness. The stator 153 of the m0- tor is enclosedwithin the housing shell 154. At its lower end the motor shaft 156 iscarried by a suitable thrust bearing 157. This assembly is carried bythe casting 158, which is attached to the end casting 159 of the motorhousing by suitable meanssuch as the V, threaded rods 160. A dependingextension .161 of the 162, and is retained by the central tie bar .163.The

chamber 164 formed by the housingextension 161, has its lowerendconnected to tube 166,, and alsoserves to enclose the oil reservoir167.

At its upper end the motor shaft 156 is connected by coupling168 to theshaft 169 of the centrifugal pump 152. Adjacent the coupling 168 themotor housing 154 is terminated by the closed casting 171, which mayserve to mount the terminal connector 172. The leads to the statorwinding of the motor connect with the terminal device 172.

The lower end of the pump shaft 169 is carried by the journal 173, whichin turn is mounted upon the casting 174. The space 176 enclosed by thecasting 174, encloses the coupling 168. The pressure equalizing tube 166makes connection with space 176.

The centrifugal pump consists of a multistage centrifugal impeller 178(Figure 2D) which is carried by the shaft 169, and which operates withinthe cooperating pump housing 179. The inlet passage 181'at the lower endof the housing (Figure 2E) communicates with the interior of thestrainer 182. The strainer is provided with screened openings 183,through which mud may flow for delivery upwardly into the inlet passage131 of the pump.

T he pump discharges into a chamber 184 at its upper end, and thischamber in turn connects with the pipes 186. These pipes are bent toextend downwardly about the pump housing, below which they connect withthe ipes 147a. It will be evident that these pipes are acccrnmodatedwithin the space between the pump and motor housings and the outertubular housing 142.

With the arrangement described above, the pump delivers mud to the fluidpressure operated motor 141,

7 thus causing this motor to supply sufficient torque for rotation ofthe drill head through the gearing 146 Atthe-s m t e t e-mud discharge-t omtthe.mot tt fl i -.d 1iv re ownwar y t to shd e pa sages 0 ei rseparator 137before entering the strainer andthe pump.

Thus referring to Figure .--2C, theupper endof the outer tubular-housing 142 mounts a;closure ;191 that is provided witha taperedcentral bore. This bore seats the tapered extension-192 from the casting193," the latter .forming the lower; end of the bailer 137,- and beingattached to the bailer housing 194. The upper end of the bailer housing194is provided with,slots.196 for inflow of,,mud from the.well,;whereby-su ch mud ;flows downwardlyihrough the housing .194,andparticularly through .198 communicateswithathe passage;199 in thecasting 193, and this in turn discharges the mud into the outer tubularhousing.142,which surrounds thepump and the electric motor, wherebysuchmud fillsthe spaces between thepump and motor housings and the outerhousings 142, and is delivered to the screened openings 183 and to theinlet passage 181 of the pump.

a The lower part of the bailer housing 194 is preferably provided withopenings 2fll normally closed by vthe gates 202. In operation-cuttingswhich are too coarse to pass through the openings in the perforatedconduit .198 accumulate in the lowerportion of the housing 194. However,when the assemblyis raised to the surface of the well, such cuttings canbe flushed out by opening the closures 202.

The terminal device 172'for the electric motor is connected to a cable203 (Figure 2E) which must be supplied with current from a suitablecurrentsupply or generator at the surface of the well. In practicethecable 203 can be extended upwardly throughvarious parts of theequipment, to ultimately extend through the coupling device 136. Thecable 204 for suspending the entire assembly can consist of a hollow.wire cable of suflicient strength to support the load, together with acentral core 206 whichforms in effect an extension of the cable 203,

and :which includes the requisite number of electrical conductors. Atthe top of the well thecable can connect with a suitable device 207which makes connections with .the various conductors, and which permitsthem to connect with the various sources of current supply. Aspreviously explained, the actuator for applying impacts to the drillhead can be supplied with 30 cycle alternating current at a suitablevoltage, The electric motor can be supplied with current of the samefrequency, and from the same supply circuit, although if desired itcanbe supplied with a separate circuit at a frequency vof, say, 60 cyclesper second.

At some convenient point along the assembly suitable means is providedto engage the side walls of the well and prevent rotation of theassembly. Asshown in Figure 26, said means can consist of arcuate shoes208 for engaging the side walls of the well and urged-outcomprisingFigures 2A-2J, inclusive, can be of the order of forty feet. The weightof the parts comprisingthe assembly can be such as to provide (whenimmersed in mud) a downward force upon the drill head sufficient forproper loading and for most efficient transfer of impact energy to theformation. Assuming an actuator operat ing with 1800 impacts per minute,this load may, for example, be of the order of 30,000 pounds.

In Figure 1 it is assumed that both the electrical actuator and themotor are being supplied withcurrent frprn ordinary rotary drilling.

' frequency to effect percussion drilling.

a common generator G. I This generator can be driven by suitable meanssuch as an engine M of the'internal combustion type. The current supplyconnections from the generator to the device 207 have been shown througha suitable control panel 211, which may indicate current, voltage,frequency and like data. e e

' Over-all operation of the equipmentdescribed above is as follows: Theentire assembly 9 is lowered into a well until the'drilling head 10comes to rest-on the bottom formation. It will be understood that inthis process it may be desirable to provide a suspending-cable insection's, which can be coupled together to provide a cable of therequisite length. The various couplings can be provided with means formaking connections between the electrical conductors. Sufficientdrilling mud of proper consistency is introduced into thewell tocompletely sub- 7 merge the equipment.

Power is now supplied to the electrical motor and the electricalactuator, whereby the 'motor delivers mud at a relatively high pressureto the w In general, the present inventionhas all of the attributes oftheequipment and method described in the 'jabove mentioned copendingapplication. Assuming that the v drill head 'is operated upon arelatively hard rocklformation, the rate of drilling with the actuatorin operation is many times the rate for the same equipmentfoperatingunder the same conditions, but without operation. the

actuator. By way of example, where the drilling rate in a rock formationis of the order of 1 inch; per hour, with the actuator in operation thedrilling rate is of the order of 10 feet or more per hour. Thisremarkable increase in drilling'speed is obtained without excess powerconsumption. No great amount of power isrequired for turning the drillhead,,because with the present assembly it is not necessary to turn along drill stern extending down through the casing. Furthermore theimpact actuation ofthe drill head reduces the torque requirer'nents forturning the head relative to the rest of the assembly. 'i p The wearupon the cutters of thedrill head is notproportional to the increase indrilling speed'attained. It appears that'for a given amountofetfectivedrilling, the

- wear upon the cutting teeth using our inventionf is substantiallylessthan for conventionalrotary drilling:

A further advantage of the drillingequipmentj and method describedherein is that it is highly effective in drilling through difiicultformations, which otherwise might make it necessary to abandon a well."Although faulting presents serious diflicultylfor conventional drillingrigs, with our invention fa ulting has little if any'eifect upondrilling efficiency, andthe drill head proceeds along the desireddirection without tending to causejbreakage of the cutters or drillhead, and with little if any. tend- .ency toward deviation'. V 7 V Ano ter advantage pointed out in said copendinga'pplication is thatconventional rotary equipment is frequently susceptible'to uneven orcontoured drillingpatterns upon the bottomformations, .which greatlydecrease drilling eificiency,and which causeexcessive wearand possibledrill breakage. Here again ourequiprnentis remarkably effective undersuch conditions Where .a-formation is encountered which, under normalconditions, would developfsuch an uneven or contoured pattern, with ourmethod and apparatus such a pattern does not develop,

" and at alltimes the pattern remains even' and for miniconventionalequipment. 7 tion can be applied to remove the unevenness; Suitable mumpossibilityrof drill breakage. This result is obtained without the-useof expensive cutterheads such ashave been developed for use inconventional rotary drilling, to minimize development of such patterns.

' Under some circumstances it maybe desirable to correct an uneven orcontoured drilling pattern, as for example where the pattern has beendeveloped by' use of In such an event our invenprocedure is to slowlylower the drill head after initial light contact with the bottomformation. This is of course accompanied by rotation of the drillhead,and operation of the electric actuator and mud circulating pump..The cutters gradually cut away the high areas of the pattern due to thepercussion andchipping action of the head as the assembly is graduallylowered, and

all unevenness has disappeared.

When. drilling through clay, or other soft formations, the electricalactuator may or may not be put into operation, depending upon the choiceof the operator. However, even under such conditions use of the actuatorgenerally facilitates drilling, particularly in that it eliminatestendency towards balling adjacent to the drill head, and it generallymakes possible a high drilling speed.

The frequency of impacts upon the bottom formation is independent ofother factors, such as the operation of the mud circulating pump. Thuselficient drilling conditions can be maintained at all levels andindependent of mud circulation.

Although in the foregoing we have referred to impacts frequency of.theor der of 1800 impactsper minute, it

' will bejevident that this can be varied depending upon surface.

drilling conditions, the size of the equipment, and the like. We believethat in all instances it is desirable to-keep this frequency above about1000'impacts per minute. It isanticipated that in some applications itmay be desirable to increase the frequency to, say, 2000impacts perminute, or more. i i 7 We claim: I

1. In well drilling equipment, mounting means adapted to be lowered into"an earth well, a cutter head including mud circulating ducts car-riedat one end of the mount ing means and adapted to operate on the bottomformation, electromagnetic means serving to apply impacts to the head ata substantially'constant frequency, said means including anelectromagnetic assembly carried by the mounting means and a piston-likecore adapted to be actuated by said assembly to apply impacts to thehead, a mud circulating pump having inlet and outlet passages carried bythe mounting means, electrical motive meansv serving to operate said mudcirculating pump, a mud passagev communicating at one end with theexterior of said mounting means and at its other end with the inletpassage of said pump, motive means serving to rotate the head relativeto the mounting means comprising a motor of the fluid pressure operatedtype having inlet and outlet pa s sages, ducts connecting the outletpassage of said pump to the inlet passage of said motor, and ductsserving to connect the outlet passage of said motor to the mudcirculating ducts formed in the head.

2. Equipmentas in claim 1 in which the pumping means comprises amulti-stage centrifugal pump.

3.. Equipment as in claim 2 together with a bailer carried by themounting means and serving to remove cuttings from the mud delivered tothe pump, said bailer having openings communicating with the exterior ofsaid mounting means and connected to the mud passage, said bailer alsoincluding a plurality of gates which are adapted to be opened wherebyaccumulated cuttings can be flushed from the bailer when the equipmentis raised to the 4. In well drilling equipment, mounting means adapt- 7ed to be lowered into a well, a cutter head including mud circulatingducts carried at one end of the mounting means and adapted to operate onthe bottom formation, electromagnetic means serving to apply impacts tothe head at a substantially constant frequency, said means including anelectromagnetic assembly carried by the mounting means and a piston-likecore adapted to be actuated by said assembly to apply impacts to thehead at a substantially constant frequency to eifect percussiondrilling, a mud circulating pump having inlet and outlet passagescarried by the mounting means, electrical motive means serving tooperate said mud circulating pump, a mud passage communicating at oneend with the exterior of said mounting means and at its other end withthe inlet passage of said pump, a motor of the fluid pressure operatedtype having inlet and outlet passages serving to rotate the headrelative to the mounting means whereby the head is rotated against aformation simultaneously as impacts are applied thereto, ductsconnecting the outlet passage of said pump to the inlet passage of saidmotor, and ducts serving to connect the outlet passage of said motor tothe mud circulating ducts formed in the head.

5. In well drilling equipment, mounting means adapted to be lowered intoa well, a cutter head including mud circulating ducts carried at one endof the mounting means and adapted to operate on the bottom formation,electromagnetic means serving to apply impacts to the head at asubstantially constant frequency, said means including anelectromagnetic assembly carried by the mounting means and a piston-likecore adapted to be actuated by said assembly to apply impacts to thehead at a substantially constant frequency to effect percussiondrilling, a mud circulating pump having inlet and outlet passagescarried by the mounting means, electrical motive means serving tooperate said pump, means for engaging the side wall of the well toprevent rotation of the mounting means comprising fluid pressureoperated shoes, said shoes including a piston in contact with thecirculating mud and adapted to be urged outwardly by the pressure of themud on the pistons, a motor of the fluid pressure type having inlet andoutlet passages serving to rotate the head relative to the mountingmeans, a mud passage communicating at one end with the exterior of saidmounting means and at its other end with the inlet passage to said pump,ducts communicating between the outlet passage of said pump and theinlet passage of said motor, said ducts having a portion incommunication with said pistons, ducts serving to connect the outletpassage of said motor to the mud circulating ducts formed in the head,and a cable adapted to extend down into the well for supporting theequipment.

6. Apparatus as in claim wherein said means serving to engage the sidewalls of the well to prevent rotation of the mounting means comprises aplurality of shoes serving to engage the side walls of the well, apiston associated with each of said shoes, cylindrical openings incommunication with the circulating mud and serving to slideably receivethe pistons whereby the mud pressure urges the shoes outwardly againstthe side wall of the well.

7. in well drilling equipment, mounting means adapted to be lowered intoan earth well, a cutter head including mud circulating ducts carried atone end of the mounting means and adapted to operate on the bottomformation, electromagnetic means serving to apply impacts to the head ata substantially constant frequency, said means including anelectromagnetic assembly carried by the mounting means and a piston-likecore adapted to be actuated by said electromagnetic assembly to applyimpacts to the head at a substantially constant frequency to eifectpercussion drilling, a mud circulating pump having inlet and outletpassages carried by the mounting means, electrical motive means servingto operate said mud circulating pump, a bailer carried by the mountingmeans and serving to remove cuttings from the circulating mud, saidbailer including a plurality of gates which are adapted to be openedwhereby accumulated cuttings may be flushed from the bailer when theequipment is raised to the surface of the earth, said bailercommunicating with the exterior of said mounting means, a mud passagecommunicating at one end with the bailer and at its other end with theinlet passage of said pump, means for engaging the side walls of theWell to prevent rotation of the mounting means, said means comprising aplurality of shoes serving to engage the side walls and a pistonassociated with each of said shoes, cylindrical openings communicatingwith the circulating mud and serving to slideably receive the pistonswhereby the mud pressure against the pistons urges the shoes outwardlyagainst the side walls of the well, motive means comprising a motor ofthe fluid pressure type having inlet and outlet passages serving torotate the head relative to the mounting means, ducts interconnectingthe outlet passage of said pump, said cylindrical openings and the inletside of said motor, and ducts serving to connect the outlet passage ofsaid motor to the mud circulating ducts formed in the head.

References Cited in the file of this patent UNITED STATES PATENTS1,477,563 Hirschfeld et al Dec. 18, 1923 1,523,629 Bullock Ian. 20, 19251,899,438 Grant Feb. 28, 1933 1,983,287 Grennell Dec. 4, 1934 2,609,182Arutunofi Sept. 2, 1952 FOREIGN PATENTS 2,443 Great Britain Ian. 26,1905

